[TechAssist] Re: Toshiba projection model TP55G90 -picture all messed up!!

First, I'm using TP55g60 schematics....should be similar to your PTV.

Check microfuse F851 for 30V, weird that my schematics show it only goes to
Pins 5 and 10 of  IC751, but pin 10 of IC751 is turned on and regulated down
to 18.5 volts using the horiz drive signal from main board and goes to  the
stand up board called the Digital Convergence unit.

This signal should be present on pin 18 of Plug 701/708 and originates on
P711 pin 2.

Next you should have + and - 15V which you have, but is it present at
[4, 8, 12,and 17]<<-15 and[5 and 10] << +15V of STK 392-110??

That HD signal if present, will be processed by q764 pin 2 out/pin 3 input
from main board to Q769 base/q770base/emitter to Q771 base which outputs 18v
on the collector to provide 18 volts to pin 10 of IC751, that's in parallel
with a +15V supply switched off using D7702. Why do they need 3 extra volts
on that pin for red/green/blue horizontal convergence.....I don't know, but
that 15V supply is probably there to keep the output IC from frying.

When it comes down to it, if the Stk 392s don't fix it , get the Digital
Convergence Board. Without fail , this has been my repair method as the
output ICs on the DCB are soldered both sides and not easy to remove, if all
outputs are affected, most likely is the Q713 EEProm or the Q701 processor.
Estimate about 200.00 for this part, and get the PB board # off this as you
will need it to get the proper board.

HTH

Damon Brunger
damon101@xxxxxxxxxxxxxx
Telrad Electronic Services
Ft Wayne, IN 46815
----- Original Message -----
From: <Ttkirkpat@xxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Saturday, September 28, 2002 3:12 PM
Subject: [TechAssist] Toshiba projection model TP55G90 -picture all messed
up!!


>
> This really looks like  convergence is super bad- so bad that the menu is
not
> discernable. There are so many colored lines it almost looks like
horizontal
> out of frequency except  the lines go at different angles. Really screwy
> looking!! Anyway, the + and - 15vdc to convergence circuits is perfect as
are
> all other power sources. Sound is perfect and channels change fine. The
set
> sits upstairs so its an in-home repair. I'll change the convergence ic's
on
> general principles but has someone else seen this symptom and have a
possible
> fix I can take back with me on Monday?? Thanks for your help from Mike at
the
> Video Center. My e-mail is ttkirkpat@xxxxxxx
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